1. Field of the Invention
Exemplary embodiments of the present invention relate to a display substrate and a method of manufacturing the display substrate. More particularly, exemplary embodiments of the present invention relate to a display substrate in which a thin-film transistor (“TFT”) including an oxide semiconductor is formed and a method of manufacturing the display substrate.
2. Description of the Related Art
Generally, a liquid crystal display (“LCD”) panel includes a first substrate on which switching elements for driving each of a plurality of pixels are formed, a second substrate disposed opposite to the first substrate, and a liquid crystal layer interposed between the first and second substrates. When a voltage is applied to the liquid crystal layer, an orientation of liquid crystal molecules of the liquid crystal layer is altered to display an image.
The switching element of the LCD panel includes a gate electrode, a semiconductor pattern isolated from the gate electrode, a source electrode electrically connected to the semiconductor pattern, and a drain electrode spaced apart from the source electrode. The switching elements may be, for example, amorphous-silicon (a-Si) thin-film transistors (“TFTs”), poly-silicon (poly-Si) TFTs, oxide semiconductor TFTs, etc.
The a-Si TFT has a benefit of being readily formed in a uniform manner on large size substrates at a relatively low cost. However, the a-Si TFT undesirably has a relatively low charge mobility which may lead to threshold voltage degradation. In contrast, poly-Si TFTs have a benefit of a high charge mobility, so that deterioration of the switching element's characteristics is small in comparison with the a-Si TFT. However, a poly-Si TFT LCD device has a more complex manufacturing process than an a-Si TFT LCD, so that its manufacturing cost is undesirably higher than that of the a-Si TFT LCD.
The oxide semiconductor TFT may be manufactured in a low temperature process, and may be utilized in large size display panels. In addition, the oxide semiconductor TFT may have a high charge mobility. However, when a structure of the oxide semiconductor TFT is applied to the LCD panel in a manner similar to that in which the a-Si TFT or p-Si TFT are applied to the LCD panel, a semiconductor pattern of the oxide semiconductor TFT directly contacts with a gate insulation layer including a silicon nitride (SiNx) material disposed below the semiconductor pattern and a passivation layer disposed above the semiconductor pattern. Thus, the semiconductor pattern of the oxide semiconductor TFT is deteriorated due to the contact with the other materials, so that electrical characteristics of the oxide semiconductor TFT may be deteriorated.